1. Field of the Invention
This invention relates to a gas visualizing apparatus and a gas visualizing method, and more particularly to a gas visualizing apparatus and method for detecting gas leakage from tanks or piping in industrial plants from piping buried under or exposed from roads or the like, or outdoor or indoor piping for dwelling houses.
Such a gas visualizing apparatus and method may also be used for detecting gas leakage occurring during gas tightness tests
2. Description of the Prior Art
Conventionally, in detecting gas leakage in industrial plants, gas leak conditions are grasped through a plurality of detectors arrange in a monitoring territory. According to this method, detection is limited to an installment position of the detecting device. In order to determine leak point for large areas in an industrial plant (i.e. an amount of gas leakage and a position of a specific leaking point in a tank or piping), for example, it is necessary to install gas leak detectors in numerous locations to grasp leak conditions.
On the other hand, proposal have been made, for monitoring such gas leakage, to emit an infrared beam to a particular gas leak monitoring territory, and determine gas leakage by referring to the state in which the infrared beam is absorbed by the leaking gas. In this case, however, since the beam used is collimated, it is necessary to cause the beam to scan the monitoring territory.
The Inventors have devised a gas visualizing apparatus in which an infrared beam is emitted in a two-dimensional manner by a light emitter to cover a relatively large gas leak monitoring territory. However, such an apparatus involves great power consumption to drive the light emitter. This apparatus has a further disadvantage of requiring a large and expensive high-power laser.
It is sufficient just to detect infrared radiation from a background in a gas leak monitoring territory, and visualize gas leak conditions in the form, for example, of a variable density image on a display unit such as a CRT. However, with an apparatus have an ordinary construction, a detection signal providing gas absorption information is weak relative to a background signal, resulting in an inadequate display made on the CRT. That is, depending on the weather or season, the image may be too bright or too dark under the influence of sunlight and the like. This, a good resolution of light and shade cannot be achieved to reflect a gas concentration to be detected. However since the infrared gas absorption information of gas leakage is a dark image signal, it is difficult to clearly distinguish between this information and the background information, even if the infrared gas absorption is included in an image of the monitoring territory according to the conventional method.
This difficulty of clear distinction between the infrared gas absorption information of gas leakage an the background information occurs also where infrared radiation from the background is detected as it is, as explained hereinbefore, and where an infrared emitter is operated to emit an infrared beam, and the infrared beam radiated or reflected from the background is detected and displayed.